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CAIE A-Level Chemistry 3.6 Intermolecular Forces and Bond Properties

Practise identifying intermolecular forces and using molecular size, polarity and hydrogen bonding to explain properties.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Exam points

  • identify id–id forces in every molecular substance and add pd–pd forces for polar molecules
  • identify hydrogen bonding only when the required N–H or O–H donor and lone-pair acceptor are present
  • compare physical properties through intermolecular-force strength without confusing them with covalent bond energy

Covered syllabus points

3.6.1—Hydrogen bonding3.6.2—Electronegativity and bond polarity3.6.3—Van der Waals’ forces as the intermolecular3.6.4—That, in general, ionic, covalent and metallic

3.6 Intermolecular forces and bond properties question 1

[Maximum number: 3]

Oxygen is a Group 16 element.

Question (a)

(a)

Fig. 2.1 shows the boiling points of H2O\mathrm{H}_{2} \mathrm{O} and other Group 16 hydrides.

Fig. 2.1

Fig. 2.1

[ 3 ]

Question (i)

(i)

Explain the trend in the boiling points of the Group 16 hydrides H2 S\mathrm{H}_{2} \mathrm{~S} to H2Te\mathrm{H}_{2} \mathrm{Te}.

[ 2 ]

Question (ii)

(ii)

Explain why the boiling point of H2O\mathrm{H}_{2} \mathrm{O} is much higher than that of H2 S\mathrm{H}_{2} \mathrm{~S}.

[ 1 ]

3.6 Intermolecular forces and bond properties question 2

[Maximum number: 2]

The Pauling electronegativity values of elements can be used to predict the chemical properties of compounds.

Use the information in Table 1.1 to answer the following questions.

Table 1.1

Table 1.1

Complete Table 1.2 by placing a tick (✓)(\checkmark) to show which of the compounds have molecules with an overall dipole moment.

Table 1.2

Table 1.2

3.6 Intermolecular forces and bond properties question 3

[Maximum number: 1]

The halogens chlorine, bromine and iodine show trends in chemical and physical properties down the group.

Table 3.1 shows some properties of chlorine, bromine and iodine.

Table 3.1

Table 3.1

Iodine monobromide, IBr , is a dark red solid that melts near room temperature.

IBr reacts with propene. The mechanism for this reaction is the same as the mechanism for that of HBr with propene.

Identify all the intermolecular forces that exist between molecules of IBr .

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